Systems and methods for arc fault detection

Abstract

In accordance with one aspect the present disclosure is directed toward a method for detecting arc faults on a power line. The method may include monitoring power signals associated with a power line and filtering the power signals to produce a high frequency signal and a low frequency signal. A mask signal may generated based on the low frequency signal, and the high frequency signal may be analyzed to extract a broadband portion of the high frequency signal. A fault counter may be incremented if the magnitude of the broadband portion is approximately greater than a first threshold level. A fault counter may be decremented if the magnitude of the broadband portion is approximately less than the first threshold level. A trip signal is provided to a switching device associated with the power line if the fault counter exceeds a predetermined fault limit.

What is claimed is: 
     
       1. An electrical fault detection device, comprising:
 a high-frequency sensor coupled to an electrical distribution line for detecting a high-frequency component of a sinusoidal electrical power signal, the high frequency sensor adapted to allow passage of high frequency signals and reject low frequency signals; 
 a series arc-detection circuit coupled to the high-frequency sensor and including: 
 a high-frequency module configured to identify and reject one or more narrowband portions of the high frequency component and identify a broadband portion of the high frequency component; 
 a detection module configured to:
 rectify the sinusoidal electrical power signal; 
 store a fault count value representing a propensity of the high-frequency component to be an arc fault; 
 adjust the fault count value based on at least one characteristic of the broadband portion, the at least one characteristic including one or more of a quarter-cycle amplitude of the broadband portion during the quarter cycle following a zero crossing of the rectified sinusoidal electrical power signal, a non-quarter-cycle amplitude of the broadband portion after the quarter cycle, and a rate-of-change of the amplitude of the broadband portion, wherein each of the at least one characteristic has a respective weighted adjustment factor defining an amount by which the fault count value is adjusted upon detection of the at least one characteristic; and 
 generate a series-arc trip signal if the fault count value exceeds a fault count threshold; and 
 a trip circuit responsive to the series-arc trip signal for opening the electrical distribution line. 
 
 
     
     
       2. The electrical fault detection device of  claim 1 , wherein the high-frequency module includes a superheterodyne receiver. 
     
     
       3. The electrical fault detection device of  claim 1 , further comprising:
 a low-frequency sensor coupled to the electrical distribution line for detecting a low-frequency portion of the rectified sinusoidal electrical power signal; 
 a parallel-arc detection circuit coupled to the low-frequency sensor and configured to: 
 monitor the amplitude of a current level associated with the low-frequency portion of the rectified sinusoidal electrical power signal; and 
 generate a parallel-arc trip signal if the amplitude of the current level of the low frequency portion exceeds a threshold parallel-arc current level, wherein the trip circuit is further configured to open the electrical distribution line in response to the parallel-arc trip signal. 
 
     
     
       4. The electrical fault device of  claim 3 , further comprising:
 a differential sensor electromagnetically coupled to hot and neutral lines of the electrical distribution line for detecting a differential current between the hot and neutral lines; 
 a differential fault detection circuit coupled to the differential sensor and configured to generate a differential fault trip signal if the amplitude of the differential current exceeds a threshold differential current, wherein the trip circuit is further configured to open the electrical distribution line in response to the differential fault trip signal. 
 
     
     
       5. The electrical fault device of  claim 4 , further including:
 a memory device adapted to record one or more of a series-arc trip signal, a parallel-arc trip signal, and a differential trip signal prior to an opening of the electrical distribution line; and 
 a display device adapted to display a signal indicative of one or more recorded trip signals. 
 
     
     
       6. The electrical fault detection device of  claim 4 , further configured to:
 establish a parallel arc-fault test time period; and 
 provide a test command signal to a test signal oscillator, the test signal oscillator configured to generate a test parallel arc-fault signal that is substantially similar to a parallel arc-fault condition and deliver the test parallel arc-fault signal upstream of the parallel arc-fault detection circuit; 
 wherein the trip circuit is configured to generate a test failure trip signal if the parallel arc detection circuit fails to generate the parallel arc trip signal in response to the test parallel arc-fault signal within the parallel arc-fault test time period. 
 
     
     
       7. The electrical fault detection device of  claim 6 , further configured to prevent the trip circuit from opening the electrical distribution line resulting
 from the parallel arc trip signal generated in response to the test parallel arc-fault signal during parallel arc-fault test time period. 
 
     
     
       8. The electrical fault detection device of  claim 7 , further configured to:
 establish a differential fault test time period; and 
 provide the test command signal to a CFO stimulus oscillator, the GFCI stimulus oscillator configured to:
 generate a test differential fault signal that is substantially similar to a differential fault condition; and 
 deliver the test ground fault signal to a test port of the differential fault detection circuit; 
 
 wherein the trip circuit is configured to generate the test failure trip signal if the differential fault detection circuit fails to generate the differential fault trip signal in response to the test differential fault signal within the differential fault test time period. 
 
     
     
       9. The electrical fault detection device of  claim 1 , wherein the detection module is configured to establish a zero-crossing time period representing the time period that the amplitude of the rectified sinusoidal electrical power signal is below a threshold level. 
     
     
       10. The electrical fault detection device of  claim 9 , wherein the threshold current level is selected such that the zero-crossing time period is about 2 milliseconds. 
     
     
       11. An electrical fault detection device, comprising:
 a high-frequency sensor coupled to an electrical distribution line for detecting a high-frequency component of a sinusoidal electrical power signal; 
 a series arc-detection circuit coupled to the high-frequency sensor and including: 
 a high-frequency module configured to identify a broadband portion of the high frequency component; 
 a detection module configured to:
 rectify the sinusoidal electrical power signal; 
 store a fault count value representing a propensity of the high-frequency component to be an arc fault; 
 adjust the fault count value based on at least one characteristic of the broadband portion, the at least one characteristic including one or more of a quarter-cycle amplitude of the broadband portion during the quarter cycle following a zero crossing of the rectified sinusoidal electrical power signal, a non-quarter-cycle amplitude of the broadband portion after the quarter cycle, and a rate-of-change of the amplitude of the broadband portion, wherein each of the at least one characteristic has a respective weighted adjustment factor defining an amount by which the fault count value is adjusted upon detection of the at least one characteristic; and 
 generate a series-arc trip signal if the fault count value exceeds a fault count threshold; and 
 
 a trip circuit responsive to the series-arc trip signal for opening the electrical distribution line 
 wherein the detection device is further configured to:
 determine a dynamic range of the broadband portion; and 
 decrease the fault count value if the dynamic range of the broadband portion does not exceed a threshold dynamic range. 
 
 
     
     
       12. An electrical fault detection device, comprising:
 a high-frequency sensor coupled to an electrical distribution line for detecting a high-frequency component of a sinusoidal electrical power signal; 
 a series arc-detection circuit coupled to the high-frequency sensor and including: 
 a high-frequency module configured to identify a broadband portion of the high frequency component; 
 a detection module configured to:
 rectify the sinusoidal electrical power signal; 
 store a fault count value representing a propensity of the high-frequency component to be an arc fault; 
 adjust the fault count value based on at least one characteristic of the broadband portion, the at least one characteristic including one or more of a quarter-cycle amplitude of the broadband portion during the quarter cycle following a zero crossing of the rectified sinusoidal electrical power signal, a non-quarter-cycle amplitude of the broadband portion after the quarter cycle, and a rate-of-change of the amplitude of the broadband portion, wherein each of the at least one characteristic has a respective weighted adjustment factor defining an amount by which the fault count value is adjusted upon detection of the at least one characteristic; and 
 generate a series-arc trip signal if the fault count value exceeds a fault count threshold; and 
 
 a trip circuit responsive to the series-arc trip signal for opening the electrical distribution line 
 wherein the detection module is configured to establish a zero-crossing time period representing the time period that the amplitude of the rectified sinusoidal electrical power signal is below a threshold level, and 
 wherein the detection module is further configured to:
 decrease the fault count value at a first rate while the quarter-cycle amplitude at the end of the zero-crossing time period does not exceed a first amplitude threshold. 
 
 
     
     
       13. The electrical fault detection device of  claim 12 , wherein at the end of the zero-crossing time period includes about 200-400 microseconds after the end of the zero-crossing time period. 
     
     
       14. The electrical fault detection device of  claim 12 , wherein the detection module is further configured to:
 decrease the fault count value at a second rate while the non-quarter-cycle amplitude outside the zero-crossing time period is less than a second amplitude threshold, wherein the second rate is less than the first rate. 
 
     
     
       15. The electrical fault detection device of  claim 14 , wherein the detection module is further configured to;
 increase the fault count value at the second rate while the non-quarter-cycle amplitude outside the zero-crossing time period is greater than the second amplitude threshold. 
 
     
     
       16. The electrical fault detection device of  claim 15 , wherein the detection module is further configured to:
 decrease the fault count value at a third rate while the rate-of-change is less than a slope threshold outside the zero crossing period, wherein third rate is greater than first the first rate. 
 
     
     
       17. The electrical fault detection device of  claim 16 , wherein the detection module is further configured to:
 identify a peak of the rate-of-change; 
 hold the peak rate-of-change to produce a decaying peak hold signal; and 
 prevent increase of the fault count value if the decaying slope reference signal is less than a peak hold threshold. 
 
     
     
       18. An electrical fault detection device, comprising:
 a high-frequency sensor coupled to an electrical distribution line for detecting a high-frequency component of a sinusoidal electrical power signal; 
 a series arc-detection circuit coupled to the high-frequency sensor and including: 
 a high-frequency module configured to identify a broadband portion of the high frequency component; 
 a detection module configured to:
 rectify the sinusoidal electrical power signal; 
 store a fault count value representing a propensity of the high-frequency component to be an arc fault; 
 adjust the fault count value based on at least one characteristic of the broadband portion, the at least one characteristic including one or more of a quarter-cycle amplitude of the broadband portion during the quarter cycle following a zero crossing of the rectified sinusoidal electrical power signal, a non-quarter-cycle amplitude of the broadband portion after the quarter cycle, and a rate-of-change of the amplitude of the broadband portion, wherein each of the at least one characteristic has a respective weighted adjustment factor defining an amount by which the fault count value is adjusted upon detection of the at least one characteristic; and 
 generate a series-arc trip signal if the fault count value exceeds a fault count threshold; and 
 
 a trip circuit responsive to the series-arc trip signal for opening the electrical distribution line 
 wherein the detection module is configured to establish a zero-crossing time period representing the time period that the amplitude of the rectified sinusoidal electrical power signal is below a threshold level, and 
 wherein the detection module is further configured to:
 detect a number of instances that the quarter-cycle amplitude and the non-quarter-cycle amplitude collectively cross a first amplitude threshold after the zero-crossing time period; and 
 decrease the fault count value by a first rate if the number of instances exceeds a first threshold crossing limit. 
 
 
     
     
       19. The electrical fault detection device of  claim 18 , wherein the detection module is further configured to:
 detect a number of instances that the quarter-cycle and the non-quarter-cycle amplitude collectively cross a second amplitude threshold after the zero-crossing time period; and 
 decrease the fault count by the first if the number of instances that the amplitude of the broadband portion exceeds a second threshold crossing limit. 
 
     
     
       20. The electrical fault detection device of  claim 19 , wherein the first amplitude threshold is less than the second amplitude threshold and the first threshold crossing limit is less than the second threshold crossing limit. 
     
     
       21. An electronic circuit for detecting series arcing conditions in a sinusoidal electrical signal, comprising:
 a rectifier configured to obtain the absolute value of the sinusoidal electrical signal; 
 a superheterodyne receiver configured to extract a broadband component from the rectified sinusoidal signal; 
 a counter coupled to the receiver and configured to change a fault count value, the fault count value representing a propensity of the sinusoidal signal to include a series arcing condition, the change occurring at multiple rates based on one or more of a quarter-cycle amplitude of the broadband component during the quarter cycle following a zero crossing of the rectified sinusoidal signal, a non-quarter-cycle amplitude of the broadband component after the quarter cycle, and a rate-of-change of the amplitude of the broadband component; and 
 a comparator coupled to counter for generating a series-arc trip signal when fault exceeds a fault count threshold. 
 
     
     
       22. The electronic circuit of  claim 21 , wherein the counter decrements and the rate is higher when the quarter-cycle amplitude does not exceed a first amplitude threshold than when the non-quarter-cycle amplitude does not exceed the first amplitude threshold. 
     
     
       23. The electronic circuit of  claim 21 , wherein the counter decrements and the rate is higher when the quarter-cycle amplitude and the non-quarter-cycle amplitude collectively exceed a crossover threshold a predetermined number of times than when the non-quarter-cycle amplitude does not exceed the first amplitude threshold. 
     
     
       24. The electronic circuit of  claim 22 , wherein the electronic circuit comprises an ASIC and a microprocessor. 
     
     
       25. A method for electrical fault detection comprising:
 detecting a high-frequency component of a sinusoidal electrical power signal; 
 identifying a broadband portion of the high-frequency component; 
 storing a fault count value representing a propensity of the high-frequency component be an arc fault; 
 adjusting the fault count value based on at least one characteristic of the broadband portion, the at least one characteristic including one or more of the amplitude of broadband portion during power signal, the amplitude of the broadband portion after the rising quarter cycle, and a rate of change of the amplitude of the broadband portion, wherein the at least one characteristic corresponds with a weighted adjustment factor, the weighted adjustment factor defining an amount by which the fault count value is adjusted upon detection of the at least one characteristic; 
 generating a trip signal if the fault count value exceeds a fault count threshold; and 
 providing the trip signal to a trip circuit for opening the electrical distribution line in response to the trip signal. 
 
     
     
       26. An electrical fault detection device, comprising:
 a high-frequency sensor coupled to an electrical distribution line for detecting a high-frequency component of a sinusoidal electrical power signal; 
 a series arc-detection circuit coupled to the high-frequency sensor and including: 
 a high-frequency module configured to identify a broadband portion of the high frequency component; 
 a detection module configured to:
 rectify the sinusoidal electrical power signal; 
 store a fault count value representing a propensity of the high-frequency component to be an arc fault; 
 adjust the fault count value based on at least one characteristic of the broadband portion, the at least one characteristic including one or more of a quarter-cycle amplitude of the broadband portion during the quarter cycle following a zero crossing of the rectified sinusoidal electrical power signal, a non-quarter-cycle amplitude of the broadband portion after the quarter cycle, and a rate-of-change of the amplitude of the broadband portion, wherein each of the at least one characteristic has a respective weighted adjustment factor defining an amount by which the fault count value is adjusted upon detection of the at least one characteristic; and 
 generate a series-arc trip signal if the fault count value exceeds a fault count threshold; and 
 
 a trip circuit responsive to the series-arc trip signal for opening the electrical distribution line
 wherein the series arc detection circuit configured to: 
 provide a test command signal to an RF noise generator, the RF noise generator configured to generate a high-frequency broadband noise signal and deliver the high frequency broadband noise signal to an input of the high-frequency sensor in response to the test command signal; and 
 generate a test failure trip signal if adjustment of the fault count value in response to the high-frequency broadband noise signal is inconsistent with predetermined adjustment characteristics. 
 
 
     
     
       27. The electrical fault detection device of  claim 26  wherein the high-frequency broadband noise signal is adapted to cause detection module to adjust the fault count value so as to exceed a test fault count threshold within a test process time period, wherein the test fault count value is less than the fault count value. 
     
     
       28. The electrical fault detection device of  claim 27 , the series arc detection circuit further configured to generate the test failure trip signal if the fault count value does not exceed the test fault count threshold within the test process time period. 
     
     
       29. The electrical fault detection device of  claim 27 , wherein the high-frequency broadband noise signal is substantially similar to a signal generated by a broadband power line communication device. 
     
     
       30. The electrical fault detection device of  claim 26 , the series arc detection circuit further configured to provide the test command signal to the RF noise generator in response to a user-prompted test request. 
     
     
       31. The electrical fault detection device of  claim 26 , the series arc detection circuit further configured to automatically provide the test command signal to the RF noise generator at predetermined intervals. 
     
     
       32. The electrical fault detection device of  claim 26 , further comprising:
 a memory device adapted to record the test failure trip signal prior to an opening of the electrical distribution line; and 
 a display device adapted to display a signal indicative of the test failure trip signal. 
 
     
     
       33. A method for testing an electrical fault detection device having a microprocessor and analog processing circuitry, the analog processing circuitry configured to detect a high-frequency component of a sinusoidal electrical power signal, identify a broadband portion of the high frequency component, and generate digital signals indicative of at least one characteristic of the broadband portion,
 the microprocessor configured to store a fault count value representing a propensity of the high-frequency component to be an arc fault, adjust the fault count value based on the at least one characteristic of the broadband portion, and generate a trip signal if the fault count exceeds a fault threshold, the method comprising:
 providing a test command signal to an RF generator, the RF generator configured to generate, in response to the test command signal, a high-frequency broadband noise signal and deliver the high-frequency broadband noise signal to an input of the analog processing circuitry; 
 monitoring, by the microprocessor, the high-frequency broadband noise signal to determine whether the digital signals generated by the analog processing circuitry are consistent with the high-frequency broadband noise signal; and 
 generating a test failure trip signal if the digital signals generated by the analog processing circuitry are not consistent with the high-frequency broadband noise signal. 
 
 
     
     
       34. The method of  claim 33 , further including:
 performing, by the microprocessor, a microprocessor health test that includes at least one of a cyclic redundancy check and a checksum routine; and 
 providing a status confirmation signal to a microprocessor health monitoring subsystem of the analog processing circuitry if the microprocessor health test indicates that the microprocessor is operating within predefined operational specifications. 
 
     
     
       35. The method of  claim 34 , further including displaying the status confirmation signal on a display device associated with the electrical fault detection device. 
     
     
       36. The method of  claim 34 , further including resetting by the microprocessor health monitoring subsystem of the analog processing circuitry, microprocessor if status confirmation signal is not received in the microprocessor health monitoring subsystem during a predefined time interval. 
     
     
       37. The method of  claim 36 , further including:
 performing the microprocessor health test upon reset of the microprocessor; and 
 generating the test failure trip signal if (1) the microprocessor health test indicates that the microprocessor is not operating in accordance with the predefined operational specifications or (2) the status confirmation signal is not received in the microprocessor health monitoring subsystem during a predefined time interval. 
 
     
     
       38. The method of  claim 33 , further including:
 recording the test failure trip signal in a memory device associated with the microprocessor; and 
 displaying, on a display device associated with the electrical fault detection device, a signal indicative of the test failure trip signal. 
 
     
     
       39. The method of  claim 33 , further including:
 establishing a test fault count value that is less than the fault count value, wherein the high-frequency broadband noise signal is adapted to cause the detection module to adjust the fault count value so as to exceed a test fault count threshold within a test process time period; and 
 generating the failure trip signal if the fault count not exceed the fault count threshold within the process time period.